Wavelength-selective actuators show multi-directional Marangoni effect–based swimming and direct measurement of driving force.

Benefiting from a photobase, an inverse opal photonic film affords a wavelength shift of more than 200 nm under irradiation.

Pneumatic artificial muscles can move continuously under the power support of air pumps, and their flexibility also provides the possibility for applications in complex environments. However, in order to achieve operation in confined spaces, the miniaturization of artificial muscles becomes crucial. Since external attachment devices greatly hinder the miniaturization and use of artificial muscles, we propose a light-driven approach to get rid of these limitations. In this study, we report a miniaturized fiber-reinforced artificial muscle based on mold editing, capable of bending and axial elongation using gas-liquid conversion in visible light. The minimum volume of the artificial muscle prepared using this method was 15.7 mm³ (d = 2 mm, l = 5 mm), which was smaller than those of other fiber-reinforced pneumatic actuators. This research can promote the development of non-tethered pneumatic actuators for rescue and exploration, and create the possibility of miniaturization of actuators.

Here, the preparation of Janus rods formed by growing silica rods on the surface of seed particles using a wet-chemical method is demonstrated, in which Fe₃O₄ microspheres are used as the seed particles. It is found that the morphology and aspect ratio of the Janus rods can be tuned by multiple experimental parameters, such as the size of the seed particles, reagent concentration and reaction time and temperature. In addition, directed assembly of the Janus rods is performed under an external magnetic field after a surface hydrophobization modification of the rods.

This communication demonstrates a facile method to detect CO ₃ ²⁻ by naked eyes through color change based on the pH dependence of inverse opal photonic crystal polymer films.